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The United States declared its independence from Great Britain on July 4, 1776.
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On April 30, 1789 George Washington became the first President of the United States.
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Proust proposed the Law of Constant Composition, it was an extremly radical law for his time. It stated that a sample of a pure compound always contain the same elements in the same proportion. And also that the samples are always the same regardless of where or how they were formed.
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Dalton contributed the atomic theory. His theory stated that matter is composed of different weight atoms and combine in simple ratios by weight.
Dalton's atomic theory is based on the following postulates:
1.All matter consists of tiny particles
2.Atoms are indestructible and unchangeable
3.Elements are characterized by the mass of there atoms
4.When Elements react, their atoms combine in simple, whole-number ratios -
The civil war began in 1861 when Confederate troops bombarded Fort Sumter.
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President Abraham Lincoln was assassinated on the evening of April 14, 1865 while attending a special preformance of "Our American Cousin."
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The Eiffel tower was built by Alexandre Gustave Eiffel. It took 2 years 2 months and 5 days to complete it.
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Thomson discovered the electron in 1895. From the discovery of the X-ray, Thomson deduced that cathode rays showed a single charge-to-mass ratio e m and must be composed of a single type of negatively charged particle, which he called "corpuscles," but Johnstone Stoney had proposed the term electron earlier in electrochemistry. Thomson aslso realized that it was also a subatomic particle, the first one to be discovered. Thomson also discovered the isotope.
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Planck birthed the idea for the Quantum Theory and can up with the Planck constant. The Planck constant can be used to find the energy of a proton. He also wrote the Law of Heat Radiation, these to put toghther would later lead Einstein and Bohr to the Quantum Theory.
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Becquerel discovered that uranium spontaneously emits radiation. He placed a sample of uranium and black paper in a paper bag and upon mistake discovered days latter the black paper had been exposed to radiation.
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Thomson proposed the plum pudding atomic model in 1904. The mater is positively chargered which is the "pudding" and the electrons, which are negatively charged, are the "plums."
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Millikan determind the unit charge of an electron to be 1.60*10 rised to the -19. The chage of an electron can be used to calculate mass.
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Rutherford's model was created in 1911 and it consisted of a small positively charged nucleus in the middle and electrons round it.
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Rutherford was the first to split an atom and consequently discovered that uranium could be used to tell the age of things. By using the decay rate of uranium and telling how much of it was left in the sample the relative age could be told. Rutherford also was the first to propose the idea of Alpa and Beta rays come off radioactive materials. However one of his most noted acomplishments was the discovery of the nucleus and proposal of the Nuclear Model.
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Neils Bohr expanded Ernest Rutherford's findings on the structure of the atom. Bohr postulated that electrons orbit around the atom's nucleus in 1913. He also explained how electrons emit or absorb energy.
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This a hydrogen model represented by the Bohr model. It includes shells that show electrons orbits.
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The quantum model got ride of Bohr's orbital paths and replaced tham with waves.
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Heisenberg discovers Quantum Mechanics and the uncertainty principle of the quantum theory.
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In 1926 Eriwn Schrodinger produced the wave equation that is now known as the Schrodinger equation. Erwin Schrodinger took the ideas developed by de Broglie, Heisenberg and others and put them together in one equation. When solved the equation can predict the properties and reactivities of all atoms and molecules.
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De Broglie stated the idea that both light and matter had waves. He also was the first to propose that electrons were only allowed certain orbits or that there were electron waves.
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In 1932 James Chadwick proved the existence of neutrons. This solved the jigsaw puzzle of the atom. This lead to the ldiscovery of nuclear fission and eventual lead to development of nuclear weapons and nuclear power production.
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Pearl Harbor, Hawaii, was attacked by Japanese on December 7, 1941.
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In 1963 Martin Luther ling Jr. gave his famous "I Have a Dream" speech.
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On Friday November 22, 1963 President John F. Kennedy was assasinated in Dallas Texas.
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The first cell phone was invented in 1973 by Martin Cooper.
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The first ipod was invented in 2000 by apple.
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